Herpesvirus infections occur frequently after human marrow transplantation. Fatal cytomegalovirus (CMV) infections exert a major limiting influence on the overall success rate of marrow transplantation, while herpes simplex virus (HSV) and varicella zoster virus (VZV) infections add to the morbidity and mortality of this procedure. Studies of CMV infection after marrow transplantation have included measurement of specific antibody, but only nonspecific parameters of cellular immunity have been studied otherwise. Marrow transplant patients will be followed serially by lymphocyte transformation and interferon production to HSV, CMV and VZV antigens pre- and post-transplant to investigate the relationship of these specific cellular responses to acquisition of and recovery from these viral infections. Donors as well as recipients will be studied to define the relationship of donor immunity to risk of infection. Antibody titers and viral surveillance cultures will also be followed. The objective of these immunologic studies is to better characterize the cell-mediated response to these specific viral antigens and to identify risk factors that may be subject to modification. Prophylactic and/or therapeutic trials of hyperimmune globulin to CMV (CMvig) and human leukocyte interferon will also be conducted. It has been shown previously that patients with high CMV antibody titers are at a lower risk of acquiring fatal CMV infection; the CMVig study will be conducted as a randomized trial. A toxicity trial of interferon, a known marrow suppressant, will be conducted to define its potential usefulness as a antiviral agent marrow transplant; subsequent therapeutic or prophylactic trials will be used on the results.